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Lecture 1
Internet Overview: roadmap
1.1 What is the Internet?1.2 Network edge
end systems, access networks, links
1.3 Network core network structure, circuit switching, packet switching
1.4 Delay, loss and throughput in Internet1.5 Protocol layers, service models1.6 Networks under attack: security
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Lecture 1
How is the Internet Organized
A hierarchical structure. hosts combine to form a Local Area
Network (LAN). LANs combine to form an Autonomous
System (AS) Autonomous Systems combine to form
the Internet.
Internetworked networks – Internet !
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Lecture 1
What’s the Internet: “nuts and bolts” view
millions of connected computing devices: hosts = end systems running network
apps Home network
Institutional network
Mobile network
Global ISP
Regional ISP
router
PC
server
wirelesslaptop
cellular handheld
wiredlinks
access points
communication links fiber, copper,
radio, satellite transmission
rate = bandwidth
routers: forward packets (chunks of data)
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Lecture 1
What’s the Internet: “operational” view
Internet: “network of networks” Requires sending,
receiving of messages
protocols control sending, receiving of messages e.g., TCP, IP, HTTP, Skype,
Ethernet etc.
Design of protocols is the key for Internet
Home network
Institutional network
Mobile network
Global ISP
Regional ISP
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Lecture 1
What’s the Internet: an operational view
a human protocol and a computer network protocol:
human protocol
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2:00
time
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Lecture 1
human protocols:
… specific msgs sent… specific actions
taken when msgs received, or other events
network protocols: machines rather than
humans all communication
activity in Internet governed by protocols
What’s the Internet: an operational view
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Lecture 1
What’s a protocol?a human protocol and a computer network protocol:
Internet protocol example
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Got thetime?
2:00
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Get http://jjcweb.jjay.cuny.edu/ssengupta/slide.ppt
<file>time
human protocol
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Lecture 1
Thus protocols define• format, order of messages sent
and received among network entities,
• actions taken on message transmission and receipt
• address conflicts among network entities
What’s the Internet: an operational view
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Lecture 1
We have studied a high-level overview of the Internet!
Now, A closer look at the Internet structure!
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Lecture 1
Components of Internet:
Hosts (end-users) e.g. computers
access networks, physical media: wired, wireless communication links network core: interconnected
routers network of
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Lecture 1
The network edge: End-users (hosts):
run application programs e.g. Web, email
client/server
peer-peer
client/server model client host requests,
receives service from always-on server
e.g. Web browser/server; email client/server peer-peer model:
minimal (or no) use of dedicated servers
e.g. Skype, BitTorrent
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Lecture 1
Access networks and physical media
Q: How to connect end systems to edge router?
residential access nets
institutional access networks (school, company)
mobile access networks
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Lecture 1
Residential access: point to point access
Dialup via modem up to 56Kbps direct access
to router (conceptually)
ADSL: asymmetric digital subscriber line up to 1 Mbps home-to-router up to 8 Mbps router-to-home ADSL deployment:
happening
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Lecture 1
Residential access: cable modems
HFC: hybrid fiber coax asymmetric: up to 10Mbps upstream, 1
Mbps downstream network of cable and fiber attaches homes to
ISP router shared access to router among home issues: congestion
deployment: available via cable companies, e.g., MediaOne, CableVision
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Lecture 1
Institutional access: local area networks
company/univ local area network (LAN) connects end system to edge router
Ethernet: shared or dedicated
cable connects end system and router
10 Mbps, 100Mbps, Gigabit Ethernet
deployment: institutions, home LANs happening now
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Lecture 1
Wireless access networks
shared wireless access network connects end system to router
wireless LANs: radio spectrum replaces
wire e.g., 802.11b/g (WiFi):
11 or 54 Mbps
wider-area wireless access next up (?): WiMAX
(10’s Mbps) over wide area
basestation
mobilehosts
router
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Lecture 1
The Client/Server Model Client/server model is a basic design for
Internet applications server - is the information provider client - is the information consumer
example web server and a client running web browser a CNN web server simultaneously serves
thousands of clients.
In this class, we will also learn how to construct Web pages at the client end!
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What is Internet? Components… Operational view… System (structure) view… Client-server and peer to peer model…
Access Networks…
Lecture 1
Summary: What have we learnt?
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Lecture 1
Next Up…
1.1 What is the Internet?1.2 Network edge
end systems, access networks, links
1.3 Network core network structure, circuit switching, packet switching
1.4 Delay, loss and throughput in Internet1.5 Protocol layers, service models1.6 Networks under attack: security
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